Membrane depolarization-induced contraction of rat caudal arterial smooth muscle involves Rho-associated kinase

Mitsuo MITA*1, Hayato YANAGIHARA*, Shigeru HISHINUMA*, Masaki SAITO* and Michael P. WALSH.

*Department of Pharmacodynamics, Meiji Pharmaceutical University, 2-522-1 Noshio, Kiyose, Tokyo 204-8588, Japan, and .Canadian Institutes of Health Research Group in Regulation of Vascular Contractility and Smooth Muscle Research Group, Department of Biochemistry and Molecular Biology, Faculty of Medicine, University of Calgary, Calgary, Alberta T2N 4N1, Canada

Abstract

Depolarization of the sarcolemma of smooth muscle cells activates voltage-gated Ca²⁺ channels, in¯ux of Ca²⁺ and activation of cross-bridge cycling by phosphorylation of myosin catalysed by Ca²⁺}calmodulin-dependent myosin light-chain kinase (MLCK). Agonist stimulation of smooth muscle contraction often involves other kinases in addition to MLCK. In the present study, we address the hypothesis that membrane depolarization-induced contraction of rat caudal arterial smooth muscle may involve activation of Rho-associated kinase (ROK). Addition of 60 mM K⁺ to de-endothelialized muscle strips in the presence of prazosin and propranolol induced a contraction that peaked rapidly and then declined to a steady level of force corresponding to approx. 30% of the peak contraction. This contractile response was abolished by the Ca²⁺-channel blocker nicardipine or the removal of extracellular Ca²⁺. An MLCK inhibitor (ML-9) inhibited both the phasic and tonic components of K⁺-induced contraction. On the other hand, the ROK inhibitors Y-27632 and HA-1077 abolished the tonic component of  K⁺-induced contraction,

Key words: HA-1077, ML-9, myosin phosphorylation, myosin light-chain kinase, Y-27632.

Sumber : Biochem. J. (2002) 364, 431±440

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